[dm-devel] Kernel panic in dm-thin

[Demi Marie Obenour]

I got this kernel panic earlier today.  It appears to be related to
dm-thin.  In case it matters, I have a bunch of VMs that use mounts with
the 'discard' option set, so there was likely a LOT of discard activity.

I worked around the problem by disabling the feature with lvchange, but
it obviously should still be fixed.  Panic message and stack trace
attached.
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab
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<1>[13053.503343] BUG: kernel NULL pointer dereference, address: 0000000000000014
<1>[13053.503353] #PF: supervisor read access in kernel mode
<1>[13053.503357] #PF: error_code(0x0000) - not-present page
<6>[13053.503362] PGD 0 P4D 0 
<4>[13053.503365] Oops: 0000 [#1] SMP NOPTI
<4>[13053.503370] CPU: 3 PID: 50805 Comm: kworker/u8:3 Tainted: G        W         5.15.52-1.fc32.qubes.x86_64 #1
<4>[13053.503377] Hardware name: LENOVO 20HHCTO1WW/20HHCTO1WW, BIOS N1UET43W (1.17 ) 12/13/2017
<4>[13053.503383] Workqueue: dm-thin do_worker [dm_thin_pool]
<4>[13053.503392] RIP: e030:__blkdev_issue_discard+0x165/0x2a0
<4>[13053.503400] Code: 14 48 c7 c2 e0 d8 66 83 31 f6 e8 e6 1e ff ff 49 89 c6 4d 85 ff 74 13 4c 89 ff 48 89 c6 e8 f3 03 ff ff 4c 89 ff e8 ab 75 ff ff <41> 0f b7 46 14 4d 89 66 20 89 c1 80 e5 f7 66 41 89 4e 14 4d 39 6e
<4>[13053.503412] RSP: e02b:ffffc90042e2fb40 EFLAGS: 00010246
<4>[13053.503416] RAX: 0000000000000000 RBX: 0000000000000200 RCX: 00000000000000c8
<4>[13053.503422] RDX: 0000000000000001 RSI: 0000000000000200 RDI: ffffffff8366d8f8
<4>[13053.503427] RBP: 0000000000000200 R08: 0000000000000200 R09: 000000000000073c
<4>[13053.503434] R10: ffffffff812a97e8 R11: 000000000000000b R12: 000000002c7de000
<4>[13053.503439] R13: ffff888004482580 R14: 0000000000000000 R15: 0000000000000000
<4>[13053.503450] FS:  0000000000000000(0000) GS:ffff88807d380000(0000) knlGS:0000000000000000
<4>[13053.503456] CS:  e030 DS: 0000 ES: 0000 CR0: 0000000080050033
<4>[13053.503460] CR2: 0000000000000014 CR3: 00000000146a2000 CR4: 0000000000050660
<4>[13053.503469] Call Trace:
<4>[13053.503472]  <TASK>
<4>[13053.503476]  passdown_double_checking_shared_status.constprop.0+0x11b/0x140 [dm_thin_pool]
<4>[13053.503485]  process_prepared_discard_passdown_pt1+0xc4/0x190 [dm_thin_pool]
<4>[13053.503494]  break_up_discard_bio+0x152/0x270 [dm_thin_pool]
<4>[13053.503501]  process_discard_cell_passdown+0x37/0x50 [dm_thin_pool]
<4>[13053.503508]  process_discard_bio+0xf3/0x160 [dm_thin_pool]
<4>[13053.503514]  process_thin_deferred_bios+0x15d/0x240 [dm_thin_pool]
<4>[13053.503522]  process_deferred_bios+0x2d/0x1d0 [dm_thin_pool]
<4>[13053.503529]  do_worker+0xcc/0x130 [dm_thin_pool]
<4>[13053.503535]  process_one_work+0x1f1/0x390
<4>[13053.503540]  worker_thread+0x4c/0x310
<4>[13053.503543]  ? process_one_work+0x390/0x390
<4>[13053.503547]  kthread+0x127/0x150
<4>[13053.503552]  ? set_kthread_struct+0x40/0x40
<4>[13053.503557]  ret_from_fork+0x22/0x30
<4>[13053.503563]  </TASK>
<4>[13053.503565] Modules linked in: loop intel_rapl_msr ee1004 iTCO_wdt intel_pmc_bxt mei_hdcp iTCO_vendor_support intel_rapl_common snd_hda_codec_hdmi intel_powerclamp snd_ctl_led snd_hda_codec_realtek snd_hda_codec_generic snd_hda_intel snd_intel_dspcfg snd_intel_sdw_acpi snd_hda_codec snd_hda_core snd_hwdep snd_seq pcspkr joydev snd_seq_device think_lmi intel_wmi_thunderbolt firmware_attributes_class wmi_bmof snd_pcm i2c_i801 i2c_smbus vfat thinkpad_acpi fat mei_me platform_profile mei snd_timer ledtrig_audio idma64 rfkill intel_pch_thermal snd soundcore xenfs fuse ip_tables dm_thin_pool dm_persistent_data dm_bio_prison dm_crypt trusted asn1_encoder crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel serio_raw i915 nouveau nvme drm_ttm_helper mxm_wmi i2c_algo_bit ttm drm_kms_helper nvme_core cec drm wmi i2c_hid_acpi video i2c_hid pinctrl_sunrisepoint xen_acpi_processor xen_privcmd xen_pciback xen_blkback xen_gntalloc xen_gntdev xen_evtchn
<4>[13053.503645] CR2: 0000000000000014
<4>[13053.503649] ---[ end trace f86fa19611542bfa ]---
<4>[13053.772527] RIP: e030:__blkdev_issue_discard+0x165/0x2a0
<4>[13053.772545] Code: 14 48 c7 c2 e0 d8 66 83 31 f6 e8 e6 1e ff ff 49 89 c6 4d 85 ff 74 13 4c 89 ff 48 89 c6 e8 f3 03 ff ff 4c 89 ff e8 ab 75 ff ff <41> 0f b7 46 14 4d 89 66 20 89 c1 80 e5 f7 66 41 89 4e 14 4d 39 6e
<4>[13053.772556] RSP: e02b:ffffc90042e2fb40 EFLAGS: 00010246
<4>[13053.772561] RAX: 0000000000000000 RBX: 0000000000000200 RCX: 00000000000000c8
<4>[13053.772567] RDX: 0000000000000001 RSI: 0000000000000200 RDI: ffffffff8366d8f8
<4>[13053.772572] RBP: 0000000000000200 R08: 0000000000000200 R09: 000000000000073c
<4>[13053.772577] R10: ffffffff812a97e8 R11: 000000000000000b R12: 000000002c7de000
<4>[13053.772582] R13: ffff888004482580 R14: 0000000000000000 R15: 0000000000000000
<4>[13053.772593] FS:  0000000000000000(0000) GS:ffff88807d380000(0000) knlGS:0000000000000000
<4>[13053.772599] CS:  e030 DS: 0000 ES: 0000 CR0: 0000000080050033
<4>[13053.772604] CR2: 0000000000000014 CR3: 00000000146a2000 CR4: 0000000000050660
<0>[13053.772625] Kernel panic - not syncing: Fatal exception
<0>[13053.772635] Kernel Offset: disabled
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